In vitro studies of human ciliary activity require relatively large quantities of specimens of healthy ciliated epithelium. For this reason we investigated whether cryopreserved healthy mucosa taken from the sphenoid sinus during pituitary surgery would meet the demands of this type of study. The sinus mucosa from ten patients was immersed in two different cryopreservatives. One solution contained 10% dimethylsulfoxide (DMSO) as cryoprotector. The other contained glycerol as a part of human sperm preservation medium (HSPM). The ciliary beat frequency (CBF) was measured sequentially by a photoelectrical method: when specimens were fresh and then at intervals of 1 week, 1 month and 3 months after cryopreservation in liquid nitrogen and thawing. Mean CBF values recorded after thawing did not differ significantly from the values measured before cryopreservation. Prior to cryopreservation and after thawing, CBF did not change during a period of 4 h. Epithelia preserved in DMSO demonstrated that the low mean CBF (5.4 Hz) found was caused by a reversible ciliostatic effect of the medium. After thawing and rinsing with a neutral medium, CBF showed normal values. We conclude that sphenoid sinus mucosa is an appropriate source of ciliated mucosa for in vitro experiments. Since non-pathological ciliated epithelium can be maintained in a "mucosa bank," our finding makes further studies of CBF of normal human respiratory epithelium in vitro a realistic goal.